Processes of sterilizing or disinfecting fluids using gases that are evolved by electrolysis (e.g., disinfection of municipal water with chlorine gas, decomposition of organic matter in water with ozone gas, or disinfection of water with ozone gas) are common in the art. More recently, commercial methods of purification have become feasible in which COD (chemical oxygen demand) components can be removed from enriched aqueous solutions using only oxygen or ozone without adding any other agent, as described in U.S. Pat. No. 4,416,747. This approach has several advantages and holds promise in practical applications: first, the components that have undergone reaction will not remain as gases in the treated solution, thus, there is no need to add a special reagent to the solution; secondly, the absence of a special reagent prevents dilution of the aqueous solution under treatment.
In the methods described above, gases to be injected are introduced from an electrolytic cell through a filter and piping into a treatment vessel. In practice, however, pressure loss occurs within the piping or filter. In order to compensate for the pressure loss, a pressurizing pump or other means which increases the complexity of the equipment is necessary. To eliminate this problem, a method has been adopted in which the gases are preliminarily dissolved in water or another media and the resulting solution is mixed with the fluid of interest to cause a reaction. This method is advantageous in that a uniform reaction occurs and the gases evolved by hydrolysis are almost completely utilized. On the other hand, the volume of the fluid to be treated increases. This in turn necessitates post-treatments including reconcentration of the treated fluid.
To prevent the increase in the fluid volume, a method has been proposed wherein the fluid to be treated is directly subjected to electrolysis and the gases evolved are used to treat the fluid. This method, however, is not applicable to all of the kinds of fluids which can treated. In addition, if the fluid is corrosive, it will corrode electrode materials and other parts of the electrolytic system. Thus, the resulting contamination of the fluid necessitates periodic maintenance work.